1. Field of the Invention
This invention relates generally to a disabler circuit that disables a function of a device and, more particularly, by way of example, to a disabler circuit employing a fuse that can be selectively blown during the production phase of a device so as to disable a particular function of the device, such as a duplexing function of a printer.
2. Discussion of the Related Art
State of the art work group printers are complicated machines that are able to perform various printer related functions. For example, the Hewlett Packard 4600 series LaserJet® printers employ several layers of hardware and software for controlling the operation of the printer. The printer includes a printer engine that performs the printing operation. The printer engine includes an embedded formatter that provides the printer control and management operations. A boot strap loader (BSL) is also provided within the formatter that initiates the boot process at printer start-up in a manner that is well understood in the art. The BSL is firmware resident on a read only memory (ROM) of the formatter and supports the Peripheral Management Language (PML), which is used to provide device settings management. An input/output (I/O) application specific integrated circuit (ASIC) is also provided that performs input and output operations between the formatter, BSL, PML and the computer and other peripheral devices that the printer may be connected to.
Certain printer models, such as the LaserJet® 4600 series printers, employ a duplexing function built into the printer engine that allows the printer engine to print on both sides of a sheet of paper. The duplexing feature is a high-end option for laser printers of this type, and is not available on all models. Thus, those models that are able to perform the duplexing function, and other high level functions, are typically more expensive than other models that are not capable of performing these functions because of their ability to provide more features.
The models that do provide the duplexing function typically use a different formatter than those models that do not provide the duplexing function to allow for this difference in functionality. Because different formatters are required, there is added expense to the printer and it's manufacturing process that otherwise would not be required if a single formatter was able to be used for both models that did and didn't provide the built-in duplexing function. For example, the different formatters need to be stocked at the production facility and at the service facility, and need to be specifically identified. Also, the service personnel must know which printers do and don't have the duplexing function, and which formatter goes with the particular printer.